Determination of As(III) and total inorganic As in water samples using an on-line solid phase extraction and flow injection hydride generation atomic absorption spectrometry

Speciation of inorganic arsenic by μ-thin-layer chromatography coupled with laser ablation inductively coupled plasma mass spectrometry based on an ion imprinted polymer

An efficient strategy utilizing μ-thin layer chromatography coupled with laser ablation inductively coupled plasma mass spectrometry (μ-TLC-LA-ICP-MS) based on an IIP (ion imprinted polymer) was developed for the speciation of inorganic arsenic [As(III) and As(V)]. The characterization of the fabricated IIP was performed applying Fourier-transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). To prepare the thin layer chromatography plate, CaSO4 (as a binder) was incorporated with the IIP. Then, the surface of the TLC plate was swept by LA, which volatilized the species of arsenic from the thin layer chromatography plate which thereafter were introduced into the ICP-MS system. Various effective parameters on isolation efficiency, such as the IIP/CaSO4 mass ratio, mobile phase composition, and pH, were examined. Under optimized conditions, the developed method demonstrated a detection limit of 0.3 μg L-1 with a wide linear dynamic range of 0.2-100 μg L-1, and a relative standard deviation of 3.8. The performance of the developed method was investigated for the isolation of As(III) and As(V) in wastewater (Mouteh, Aghdareh, and Zarmehr mines) and human blood plasma real samples.

Combination of Biochar and Trichoderma harzianum Can Improve the Phytoremediation Efficiency of Brassica juncea and the Rhizosphere Micro-Ecology in Cadmium and Arsenic Contaminated Soil

Phytoremediation is an environment-friendly method for toxic elements remediation. The aim of this study was to improve the phytoremediation efficiency of Brassica juncea and the rhizosphere soil micro-ecology in cadmium (Cd) and arsenic (As) contaminated soil. A field experiment was conducted with six treatments, including a control treatment (CK), two treatments with two contents of Trichoderma harzianum (T1: 4.5 g m-2; T2: 9 g m-2), one biochar treatment (B: 750 g m-2), and two combined treatments of T1B and T2B. The results showed Trichoderma harzianum promoted the total chlorophyll and translocation factor of Brassica juncea, while biochar promoted plant biomass compared to CK. T2B treatment showed the best results, which significantly increased Cd accumulation by 187.49-308.92%, and As accumulation by 125.74-221.43%. As a result, the soil's total Cd content was reduced by 19.04% to 49.64% and total As contents by 38.76% to 53.77%. The combined amendment increased the contents of soil available potassium, phosphorus, nitrogen, and organic matter. Meanwhile, both the activity of glutathione and peroxidase enzymes in plants, together with urease and sucrase enzymes in soil, were increased. Firmicutes (dominant bacterial phylum) and Ascomycota (dominant fungal phylum) showed positive and close correlation with soil nutrients and plant potentially toxic elements contents. This study demonstrated that phytoremediation assisted by biochar and Trichoderma harzianum is an effective method of soil remediation and provides a new strategy for enhancing plant remediation efficiency.

A critical review of on-site inorganic arsenic screening methods

Approximately 94 to 220 million people worldwide are at risk of drinking well water containing arsenic > 10 µg/L, the WHO guideline value. To identify non-compliant domestic wells, assess health risks and reduce exposure, accurate and rapid on-site inorganic arsenic screening methods are desirable because all domestic wells worldwide need to be tested. Here, the principles, advantages and limitations of commonly used colorimetry, electrochemistry, and biosensing methods are critically reviewed, with the performance compared with laboratory-based benchmark methods. Most commercial kits are based on the classic Gutzeit reaction. Despite being semi-quantitative, the more recent and more expensive products display improved and acceptable accuracy and shorter testing time (∼10 min). Carried out by trained professionals, electrochemical methods are also feasible for on-site analysis, although miniaturization is desirable yet challenging. Biosensing using whole bacterial cells or bio-engineered materials such as aptamers is promising, if incorporated with function specific nanomaterials and biomaterials. Since arsenic is frequently found as arsenite in reducing groundwater and subject to oxidation during sampling, transportation and storage, on-site separation and sample preservation are feasible but the specific methods should be chosen based on sample matrix and tested before use. To eliminate arsenic exposure among hundreds of millions of mostly rural residents worldwide, we call for concerted efforts in research community and regulatory authority to develop accurate, rapid, and affordable tests for on-site screening and monitoring of arsenic in drinking water. Access to affordable testing will benefit people who are socioeconomically disadvantaged.

Determination of inorganic arsenic in algae using bromine halogenation and on-line nonpolar solid phase extraction followed by hydride generation atomic fluorescence spectrometry

Accurate, stable and fast analysis of toxic inorganic arsenic (iAs) in complicated and arsenosugar-rich algae matrix is always a challenge. Herein, a novel analytical method for iAs in algae was reported, using bromine halogenation and on-line nonpolar solid phase extraction (SPE) followed by hydride generation atomic fluorescence spectrometry (HG-AFS). The separation of iAs from algae was first performed by nonpolar SPE sorbent using Br^- for arsenic halogenation. Algae samples were extracted with 1% perchloric acid. Then, 1.5mL extract was reduced by 1% thiourea, and simultaneously reacted (for 30min) with 50μL of 10% KBr for converting iAs to AsBr₃ after adding 3.5mL of 70% HCl to 5mL. A polystyrene (PS) resin cartridge was employed to retain arsenicals, which were hydrolyzed, eluted from the PS resin with H₂O, and categorized as iAs. The total iAs was quantified by HG-AFS. Under optimum conditions, the spiked recoveries of iAs in real algae samples were in the 82-96% range, and the method achieved a desirable limit of detection of 3μgkg^-1. The inter-day relative standard deviations were 4.5% and 4.1% for spiked 100 and 500μgkg^-1 respectively, which proved acceptable for this method. For real algae samples analysis, the highest presence of iAs was found in sargassum fusiforme, followed by kelp, seaweed and laver.

Sensitive determination of As (III) and As (V) by magnetic solid phase extraction with Fe@polyethyleneimine in combination with hydride generation atomic fluorescence spectrometry

The magnetic nanomaterial Fe@polyethyleneimine (Fe@PEI) was successfully synthesized and used as an effective adsorbent material for magnetic solid phase extraction(MSPE) of As(III) and As(V) from water samples. Fe@SiO2 nanoparticles were prepared by one pot synthetic method using a borohydride reduction method, then modified with (3-chloropropyl)trimethoxysilane to obtain Fe@SiO2-Cl by chloropropylation, which was reacted with PEI to achieve Fe@polyethyleneimine (Fe@PEI). The microstructure and morphology of Fe@PEI were characterized by transmission electron microscoscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The experimental results showed that Fe@PEI demonstrated excellent adsorption for As(III) and As(V). Based on this fact, the determination method for these two arsenic species earned good limits of detection (LODs) of 0.002μgL(-1) and wide calibration curves in the concentration range from 0.008 to 0.2μgL(-1). The precisions of As (III) and As (V)were 1.95% and 2.55% (RSD, n=6), respectively. The proposed method was validated with real samples and the spiked recoveries were in the range of 82.7-98.3% and the accuracies were in the range of 2-13.3%. The results demonstrated that the developed MSPE method had good advantages such as simplicity, rapid separation, low cost, easy to reuse and high-quality analytical performances, which made it attractive for rapid and efficient extraction of inorganic arsenic species in the environmental water samples.

Ferric ion induced enhancement of ultraviolet vapour generation coupled with atomic fluorescence spectrometry for the determination of ultratrace inorganic arsenic in surface water

A novel method of ultraviolet vapour generation (UVG) coupled with atomic fluorescence spectrometry (AFS) was developed for the determination of ultratrace inorganic arsenic (iAs) in surface water.

Arsenic and antimony in water and wastewater: overview of removal techniques with special reference to latest advances in adsorption

Arsenic and antimony are metalloids, naturally present in the environment but also introduced by human activities. Both elements are toxic and carcinogenic, and their removal from water is of unquestionable importance. The present article begins with an overview of As and Sb chemistry, distribution and toxicity, which are relevant aspects to understand and develop remediation techniques. A brief review of the recent results in analytical methods for speciation and quantification was also provided. The most common As and Sb removal techniques (coagulation/flocculation, oxidation, membrane processes, electrochemical methods and phyto and bioremediation) are presented with discussion of their advantages, drawbacks and the main recent achievements. Literature review on adsorption and biosorption were focused in detail. Considering especially the case of developing countries or rural communities, but also the finite energy resources that over the world are still dependent, recent research have focused especially readily available low-cost adsorbents, as minerals, wastes and biosorbents. Many of these alternative sorbents have been presenting promising results and can be even superior when compared to the commercial ones. Sorption capacities were accurately compiled for As(III,V) and Sb(III,V) species in order to provide to the reader an easy but detailed comparison. Some aspects related to experimental conditions, comparison criteria, lack of research studies, economic aspects and adsorption mechanisms were critically discussed.

Robust electrochemical analysis of As(III) integrating with interference tests: a case study in groundwater

In Togtoh region of Inner Mongolia, northern China, groundwater encountered high concentrations As contamination (greater than 50 μg L(-1)) causes an increasing concern. This work demonstrates an electrochemical protocol for robust (efficient and accurate) determination of As(III) in Togtoh water samples using Au microwire electrode without the need of pretreatment or clean-up steps. Considering the complicated conditions of Togtoh water, the efficiency of Au microwire electrode was systematically evaluated by a series of interference tests, stability and reproducibility measurements. No obvious interference on the determination of As(III) was observed. Especially, the influence of humic acid (HA) was intensively investigated. Electrode stability was also observed with long-term measurements (70 days) in Togtoh water solution and under different temperatures (0-35 °C). Excellent reproducibility (RSD:1.28%) was observed from different batches of Au microwire electrodes. The results obtained at Au microwire electrode were comparable to that obtained by inductively coupled plasma atomic emission spectroscopy (ICP-AES), indicating a good accuracy. These evaluations (efficiency, robustness, and accuracy) demonstrated that the Au microwire electrode was able to determine As(III) in application to real environmental samples.

Method development for the determination of arsenic by sequential injection/anodic stripping voltammetry using long-lasting gold-modified screen-printed carbon electrode

An automated method has been developed for determining the concentration of inorganic arsenic. The technique uses sequential injection/anodic stripping voltammetry with a long-lasting gold-modified screen-printed carbon electrode. The long-lasting gold electrode was electrochemically deposited onto a screen-printed carbon electrode at a potential of -0.5 V vs. Ag/AgCl in a supporting electrolyte solution of 1M hydrochloric acid. Under optimal conditions and the applied potentials, the electrode demonstrated that it can be used for a long time without a renewal process. The linear range for the determination of arsenic(III) was 1-100 μg L(-1), and the limit of detection (LOD) in standard solutions was as low as 0.03 μg L(-1) for a deposition time of 120 s and sample volume of 1 mL. This method was used to determine the concentration of arsenic(III) in water samples with satisfactory results. The LOD in real samples was found to be 0.5 μg L(-1). In addition, speciation between arsenic(III) and arsenic(V) has been achieved with the proposed method using deposition potentials of -0.5 V and -1.5 V for the determination of the arsenic(III) concentration and the total arsenic concentration, respectively; the results were acceptable. The proposed method is an automated system that offers a less expensive alternative for determining trace amounts of inorganic arsenic.

Speciation of arsenic (III) and arsenic (V) based on quenching of CdS quantum dots fluorescence using hybrid sequential injection-stopped flow injection gas-diffusion system

A hybrid sequential injection-stopped flow injection system was developed for the speciation of arsenic based on the quenching of mercaptoacetic acid capped cadmium sulfide quantum dots (CdS-MAA QDs) fluorescence intensity. The analytical procedure involves the generation of arsine from As(III) by sodium borohydride in acetate buffer medium pH 6.0. The generated arsine (donor stream) diffuses across the PTFE membrane of the gas-diffusion unit into an acceptor stream and then interacts with CdS-MAA QDs. Total arsenic was determined after pre-reduction of As(V) to As(III) with 1% (m/v) mercaptoacetic acid. Concentration of As(V) in the sample solutions can be deduced from the difference of total arsenic and As(III). Optimization of the experimental conditions and instrumental parameters were investigated. Under optimal conditions, limits of detection were 20 μg L(-1) for As(III) and 40 μg L(-1) for As(V). Recoveries in the range 84-103% were obtained from sediment sample.